de·cide 
/dɪˈsaɪd/ verb
de·cides; de·cid·ed; de·cid·ing /dɪˈsaɪd/ verb 1 a : to make a choice about (something) : to choose (something) after thinking about it [+ obj] ▪ He decided that dinner would be at 7 o'clock, and asked guests to arrive at 6. — often followed by to + verb ▪ She decided to go along with us. ▪ They have decided not to leave. — often + what, where, whether, if, etc. ▪ Have you decided what you'd like for breakfast? ▪ He is having trouble deciding which school to go to. ▪ She says she'll decide by January whether (or not) to run for office. ▪ We are deciding if we should stay. [no obj] ▪ She is having difficulty deciding about the offer. ▪ I decided in favor of the other candidate. [=I chose the other candidate] ▪ Voters must decide between the two candidates. [=voters must choose one or the other candidate] ▪ You have to decide for yourself. [=you are the only one who can decide] ▪ I decided against telling her. [=I decided not to tell her]
b : to choose whether or not to believe (something) after thinking about it : to reach a conclusion about (something) because of evidence [+ obj] ▪ They decided that he was right. ▪ I am trying to decide if it's warm enough for swimming. [no obj] ▪ “Do you think she is telling the truth?” “I'm not sure. I'm still trying to decide.” 2 : to cause (something) to end in a particular way : to determine what the result of (something) will be [+ obj] ▪ A few hundred votes could decide the election. ▪ One blow decided the fight. ▪ This battle could very well decide the war. [no obj] ▪ Will the business be successful? Let the public decide. — often used as deciding ▪ the deciding game in the series [=the game that determines who wins the series] ▪ The vice president will cast the deciding vote. 3 law : to end (a court case) in a particular way : to make a judgment in a court of law [+ obj] ▪ The case will be decided by the Supreme Court. [no obj] ▪ The court decided against the defendant. [=the defendant was found guilty] ▪ The court decided in favor of the plaintiff. = (less commonly) The court decided for the plaintiff. [=the plaintiff won the case]
b : to choose whether or not to believe (something) after thinking about it : to reach a conclusion about (something) because of evidence [+ obj] ▪ They decided that he was right. ▪ I am trying to decide if it's warm enough for swimming. [no obj] ▪ “Do you think she is telling the truth?” “I'm not sure. I'm still trying to decide.”
decide on/upon [phrasal verb]
decide on/upon (something) : to choose (something) after thinking about the possible choices
▪ He decided on blue rather than green. ▪ We looked at all the cats in the pet store and finally decided on a little black-and-white one. ▪ I am having trouble deciding on a gift for them.
▪ He decided on blue rather than green. ▪ We looked at all the cats in the pet store and finally decided on a little black-and-white one. ▪ I am having trouble deciding on a gift for them.
deciding factor 1 : something that causes you to make a particular decision
▪ The deciding factor was cost. [=the decision was based on cost; the least expensive option was chosen] ▪ His lack of experience was the deciding factor in my decision not to hire him. 2 : something that causes something to end a particular way
▪ His home run was the deciding factor in the game. [=his home run won the game]
▪ The deciding factor was cost. [=the decision was based on cost; the least expensive option was chosen] ▪ His lack of experience was the deciding factor in my decision not to hire him.
▪ His home run was the deciding factor in the game. [=his home run won the game]
